One or more cylinders of a large internal combustion engine, such as a “V8” engine, may be withdrawn from firing service in order to enhance fuel efficiency under low-demand conditions by de-activating the valve train leading to pre-selected cylinders of the engine. De-activation of the valve train may be accomplished in a variety of ways, such as by using special valve lifters having internal locks that may be switched off either electronically or hydraulically, or by using a two-step valve lift arrangement having a common oil supply for the hydraulic tappets and the switchable rocker arms, or by using any other cylinder deactivation system suitable for a purpose disclosed herein employing cylinder deactivation lifters. Such switching may be accomplished using a hydraulic manifold, referred to as a Lifter Oil Manifold Assembly (LOMA), in combination with electrically driven solenoid valves to selectively pass oil to the switchable elements on command from an Engine Control Module (ECM). Such systems require an oil pressure control system that can maintain operational oil pressures at both a relatively low value where the switchable elements facilitate firing of all cylinders, and a relatively high value where the switchable elements de-activate firing of selected cylinders. The presence of air bubbles in the oil supply gallery or the oil control gallery can inadvertently affect the ability of the oil pressure control system to maintain the desired operational pressures, which could lead to pressure fluctuations in the oil control gallery that could cause inadvertent and undesirable switching of the switching elements.
Accordingly, it is desirable to provide an oil pressure control system for switchable valve train components for reducing pressure fluctuations in an oil control gallery sufficient to avoid inadvertent switching of switchable valve train components.